Prevention & care
Emergency contraception: pills, IUDs, timing and what the evidence can establish
On this page
Emergency contraception means methods used after sex to prevent pregnancy when contraception was absent or may have failed. It includes emergency pills and a copper intrauterine device in US CDC guidance. “Morning-after pill” is an imprecise name: options have different timing windows and are not confined to the next morning.[1]
Pills and devices have different roles
Levonorgestrel and ulipristal acetate are distinct emergency pill ingredients. CDC also describes a combined estrogen-progestin regimen, which is less effective and causes more nausea than the dedicated pill options. The copper IUD provides an emergency option that can continue as regular contraception. CDC discusses use as soon as possible within five days after unprotected intercourse; device timing can require additional clinical interpretation. A pharmacist or clinic can identify the relevant option promptly rather than waiting for an app to estimate ovulation.[1]
Levonorgestrel is not an abortion medicine
Plan B One-Step and its levonorgestrel generics should not be confused with medicines used for abortion. FDA’s mechanism review supports inhibition or delay of ovulation, not an effect on implantation or maintenance of an established pregnancy. This biological distinction does not establish whether a pill will work after a particular encounter: cycle timing may be uncertain, and an already completed ovulation changes the question. An app’s prediction is not evidence that ovulation has or has not occurred.[2]
Access differs by ingredient and location
The US Office on Women’s Health distinguishes nonprescription Plan B One-Step and similar generics from prescription-only ella, the ulipristal product. A clinician is needed for IUD placement. Local stock, appointment availability and payment can affect how quickly an option is obtained. This US access description is not a statement about every jurisdiction or a guarantee of insurance coverage. When comparing methods, availability within the useful window is a practical part of the decision.[3]
Evidence & uncertainty
The distinction between preventing pregnancy and ending an established pregnancy is essential. FDA explains that levonorgestrel emergency contraception acts before ovulation and does not end an existing pregnancy. Older wording about implantation was changed in 2022 because the reviewed evidence did not support that mechanism.[2]
Selected-source overview · Independent review pendingPublished questions
Is it too late if it is no longer the next morning?
Selected-source overview · Independent review pending. Read the evidence context.
Not necessarily. The useful timing depends on the method, and prompt pharmacy or clinical advice matters. The name “morning-after” can be misleading.[3]
Evidence behind this answer
- Emergency contraception
official public health explanation · Date not stated
Original official page; selected relevant passages inspected · How do I get emergency contraception? US prescription distinction; timing and coverage context
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does Plan B end an existing pregnancy?
Selected-source overview · Independent review pending. Read the evidence context.
No. FDA’s review supports an effect on ovulation and explains that Plan B does not terminate an established pregnancy.[2]
Evidence behind this answer
- Plan B One-Step Information
official public health explanation · 2022
Original official page; selected relevant passages inspected · 2022 mechanism-label change; abortion distinction; no implantation effect
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Will a previous emergency pill cover later sex?
Selected-source overview · Independent review pending. Read the evidence context.
Do not assume that. The ulipristal label notes rapid return of fertility and discusses the need for subsequent contraceptive protection.[4]
Evidence behind this answer
- ella prescribing information, 2021 revision
historical approved product label · 2021
Original historical approved label selected sections inspected; not asserted to be the latest label; current CDC guidance also checked · Sections 5.4–5.5 and 7.1; enzyme inducers, progestin interactions, rapid fertility return
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does higher body weight mean emergency pills are unsafe?
Selected-source overview · Independent review pending. Read the evidence context.
CDC distinguishes possible reduced effectiveness from safety. Evidence cannot give a certain success-or-failure answer for a particular person.[5]
Evidence behind this answer
- Appendix J: Classifications for Emergency Contraception
professional or agency guidance · 2024
Original official page; selected relevant passages inspected · Table J1: obesity, pregnancy, breastfeeding, sexual assault and CYP3A4 inducers
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Did the IUD trial prove copper IUDs never fail?
Selected-source overview · Independent review pending. Read the evidence context.
No. Zero events among 321 participants still leaves statistical uncertainty. A trial result and a universal guarantee are different claims.[6]
Evidence behind this answer
- Levonorgestrel vs Copper Intrauterine Devices for Emergency Contraception
original study · 2021
PubMed indexed original-study abstract inspected through search retrieval; full article not independently appraised · Indexed original-trial abstract: modified intention-to-treat pregnancy outcomes and absolute difference
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Are all emergency pills nonprescription in the US?
Selected-source overview · Independent review pending. Read the evidence context.
No. The Office on Women’s Health distinguishes nonprescription levonorgestrel products from prescription ella. Availability and access still vary locally.[3]
Evidence behind this answer
- Emergency contraception
official public health explanation · Date not stated
Original official page; selected relevant passages inspected · How do I get emergency contraception? US prescription distinction; timing and coverage context
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Ulipristal and regular hormones can interact
Ulipristal modifies progesterone-receptor signaling. Its FDA label discusses interactions with progestin-containing contraception and with medicines or herbal products that induce CYP3A4, a drug-metabolizing enzyme. These are reasons to disclose current contraception, prescriptions and supplements, including St John’s wort. The label also warns that fertility can return rapidly after use, so a previous emergency dose does not provide ongoing protection for later sex. Restarting a regular method needs product-specific professional guidance rather than improvising combinations.[4]
A hormonal-IUD trial adds evidence without settling every guideline
A 2021 randomized trial compared a levonorgestrel IUD with a copper IUD in people seeking emergency contraception. Pregnancy occurred in one of 317 levonorgestrel participants and none of 321 copper participants: 0.3% versus 0%, an absolute difference of 0.3 percentage points. The confidence interval for the difference ranged from −0.9 to 1.8 points. The trial supported its prespecified noninferiority conclusion; it did not establish zero risk or evaluate every hormonal-IUD formulation. CDC’s 2024 emergency-method page specifically lists copper IUDs, illustrating the need to distinguish trial evidence from guideline scope.[6]
Emergency contraception does not complete sexual-health care
Possible failure of contraception can raise more than a pregnancy-prevention question. Emergency methods do not protect against sexually transmitted infections. Following sexual assault, clinical care can also address infection risks and trauma support; CDC’s eligibility guidance discusses these circumstances separately. A person should receive an individualized follow-up plan, including pregnancy assessment when appropriate. Significant symptoms or a suspected pregnancy need clinical evaluation rather than reassurance from a previous emergency dose or a reassuring app display.[5]
Body size and medical eligibility are different questions
CDC notes that emergency pills might be less effective in people with obesity, based on limited secondary analyses. This is an effectiveness uncertainty, not evidence that emergency pills are inherently dangerous at a higher body size. The copper-IUD eligibility assessment differs from the pill assessment. Current infection, possible pregnancy and other clinical circumstances can affect device suitability. A numerical weight cutoff should not be treated as proof that a pill certainly works below it or certainly fails above it.[5]
References
- Emergency Contraception
Professional or agency guidance
US CDC · Content/publication date: 2024
Accessed: 2026-10-13 UTC · Original official page; selected relevant passages inspected
Cited sections: Types; Timing; Comments and Evidence Summary; regular contraception - Plan B One-Step Information
Official public health explanation
US FDA · Content/publication date: 2022
Accessed: 2026-10-13 UTC · Original official page; selected relevant passages inspected
Cited sections: 2022 mechanism-label change; abortion distinction; no implantation effect - Emergency contraception
Official public health explanation
US Office on Women’s Health · Content/publication date: not stated
Accessed: 2026-10-13 UTC · Original official page; selected relevant passages inspected
Cited sections: How do I get emergency contraception? US prescription distinction; timing and coverage context - ella prescribing information, 2021 revision
Historical approved product label
US FDA / product label · Content/publication date: 2021
Accessed: 2026-10-13 UTC · Original historical approved label selected sections inspected; not asserted to be the latest label; current CDC guidance also checked
Cited sections: Sections 5.4–5.5 and 7.1; enzyme inducers, progestin interactions, rapid fertility return - Appendix J: Classifications for Emergency Contraception
Professional or agency guidance
US CDC · Content/publication date: 2024
Accessed: 2026-10-13 UTC · Original official page; selected relevant passages inspected
Cited sections: Table J1: obesity, pregnancy, breastfeeding, sexual assault and CYP3A4 inducers - Levonorgestrel vs Copper Intrauterine Devices for Emergency Contraception
Original study
Turok DK and colleagues / PubMed · Content/publication date: 2021
Accessed: 2026-10-13 UTC · PubMed indexed original-study abstract inspected through search retrieval; full article not independently appraised
Cited sections: Indexed original-trial abstract: modified intention-to-treat pregnancy outcomes and absolute difference
Scope & review
- Population
- General readers; source-specific populations and eligibility are distinguished
- Exposure or intervention
- Emergency contraception
- Comparison
- Source-specific comparisons; no individual prescription or universal ranking
- Outcomes
- Definitions, subtypes, interpretation, practical context and uncertainty
- Timeframe
- Publication years and source update dates are recorded where established; sources retrieved 2026-10-13 (UTC)
- Jurisdiction
- US clinical context unless an international source is explicitly identified; access and local requirements differ
Selected-source educational explanation with source-specific limitations. No exhaustive search, independent systematic synthesis or qualified medical review.
Sources checked on their individual access dates. Selected sources were checked; ongoing surveillance and qualified review have separate statuses on the coverage page.
Revision history
- 2026-10-13 UTC: Added a selected-source educational explanation in edition 4.1; independent medical review remains pending.
What this article still leaves open
- These selected sources do not resolve every individual treatment choice or subgroup outcome.
- Independent medical review and an exhaustive evidence synthesis have not been completed.
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